(1) Field of the Invention
The present invention relates to a spin dryer for drying semiconductor materials, and more specifically to an improvement of a lid member having a filter medium to be mounted so as it opens on a spin dryer body.
(2) Description of the prior art
Spin dryers have been used for removing water droplets from semiconductor materials such as silicon wafers after being washed and drying the materials. The body of these spin dryers comprises a rotor to be driven on which semiconductor materials to be dryed are set, and a casing enclosing the rotor. Rotation of the rotor generates air flow into the rotor from thereabove and the air drawn discharges out through an exhaust duct located at the periphery of the casing. Therefore, a lid member which has an air filter medium therein is mounted so as it opens on the spin dryer body in order to filter the air to be drawn into the spin dryer body. The lid member will be opened when semiconductor materials are set into or dismounted from the rotor.
In the prior art, there has been provided a lid member such as shown, for example, in U.S. Pat. No. 5,050,316, which is shown in FIGS. 5 and 6. Such lid member on the spin dryer body comprises a case, an annular filter medium which is called a HEPA filter, a top plate on the filter medium, and a vertically movable lid plate positioned above the top plate. Also, the lid plate is provided with an annular seal attached on the lower face thereof, and bellows are provided between a peripheral wall of the case and an outer periphery of the lid.
When drying semiconductor materials by driving the rotor, the lid plate is elevated to separate the seal from the top plate so as to enable air flow into the rotor, while in stoppage of the rotor the lid plate is lowered by means of an air-cylinder to close the gap provided between the seal and the top plate so as to prevent air from being introduced.
In the conventional lid member which has the lid plate with a flat surface, when the lid member is opened after the operation of the rotor, a negative pressure will occur on the bottom side of the lid member and a turbulence of air will be generated on the top side thereof. Accordingly, air will be drawn from lower side and then introduced into the spin dryer body, which will contaminate semiconductor materials after drying.